Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses
Reexamination Certificate
2003-01-13
2004-08-17
Mai, Huy (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
C351S083000, C351S159000
Reexamination Certificate
active
06776480
ABSTRACT:
FIELD OF THE INVENTION
The present application relates to spectacles, spectacle frames and methods for providing spectacles of the wrap-around type, and, in particular, to frames adapted to receive optical lenses characterized by contour fitting with changes in base curvature across the lens.
BACKGROUND
It is known in the prior art to manufacture non-corrective eyeglasses such as sunglasses or protective eyeglasses having wrap-around segments designed to shield the eye from incident light, wind, and foreign objects in the temporal vision field of the wearer.
Visible light and light in the UV region may enter the eye from angles as high as 100° from the line of sight. There has been a need to provide sunglasses or protective eyeglasses, with a significant range of refractive powers, whilst maintaining a cosmetically acceptable appearance. The high radius of curvature required for a properly aligned ophthalmic lens including a prescription surface to enclose the wearer's eyes is such that the spectacles would produce a bug-eyed appearance, which would be cosmetically unacceptable. Fashionable eyewear incorporating wide field spherical lenses of very high curvature, such as those disclosed in U.S. Pat. No. 6,142,624 to Applicants, are positioned close to the eyes to enclose the visual field of the wearer whilst maintaining alignment of the optical axes with the direct line of sight. As disclosed in this patent frames for such lenses may be designed to lie on an extension of a spherical front surface thereof.
Applicants disclose in International Patent Application PCT/AU97/00188 “Improved Single Vision Lenses” (now U.S. Pat. No. 6,361,166), an optical lens element including a front and back surface, at least one surface being continuous, and forming a prescription (Rx) zone and a peripheral temporal zone for providing a shield in the area of the temples, which zones are smoothly blended to avoid a prismatic jump from the Rx zone to the temporal zone. These lenses are designed to be located before the wearer's eyes so that the direct line of sight intersects the optical center of the lens front surface, but the optical axes are rotated temporally in order to assist achievement of the wrap-around configuration. Such lenses have surface corrections in order to reduce optical errors within the field of vision as a result of the intended horizontal tilt.
In International Patent Application PCT/AU98/00274 “Lenses and Spectacles Bearing Lenses” (now U.S. Pat. No. 6,334,681), to Applicants, the entire disclosure of which is incorporated herein by reference, Applicants disclose an ophthalmic article including an optical lens element having a front and back surface, at least one surface being continuous, and forming a prescription (Rx) zone and optionally a non-prescription peripheral temporal zone, at least one surface exhibiting a change of base curve across the field of vision of the wearer; the front and/or back surface bearing a surface correction to at least partially adjust for optical errors. The curvature changes accentuate the lens surface shape in order to fit the contour of the wearer's face and minimize the need for tilt.
Whilst such lenses provide lens design options not heretofore available, it is necessary to provide spectacle frames for such unusually shaped lenses.
OBJECTS AND ADVANTAGES OF THE INVENTION
Applicants have investigated the topological properties of surfaces with changing base curve across a desired aperture, investigating in particular the opportunity to maintain a simple geometric form for the carrier surface on which the lens aperture is formed, despite the complexity of the surface to be intersected by the frame outline.
Most eyeglass lenses and frames are formed on spherical, cylindrical or toroidal “carrier surfaces”, meaning that the aperture outlines of the lens and the frame may be formed on a simply defined surface that is proximate the physical surface of the lens being glazed. For non-corrective lenses, the carrier surfaces and the lens front surface are usually coincident. Wrap around shields and unitary lenses may employ elliptic or high order polynomial surface forms. In this case, the lens outline is typically formed directly on the lens surface and the difficulties presented in creating a closed lens aperture are avoided by using temple bar or rimless forms of lens support. See for example U.S. Pat No.: 1,741,536 (Rayton); U.S. Pat. No. 4,859,048 (Jannard); U.S. Pat. No. 4,867,550 (Jannard); U.S. Pat. No. 5,604,547 (Davis); U.S. Pat. No. 5,774,201 (Tackles); U.S. Pat. No. 5,689,323 (Houston et al.) and; U.S. Pat. No. 5,825,455 (Fecteau et al.).
The design of prescription lenses is complicated by the need to eliminate optical errors in the oblique visual field. Specifically, the lens designer needs to observe a relationship between front surface curvature and lens through power specified by the so-called “Tscheming Ellipses” first described 100 years ago. These identify specific combinations of frontal base curvature and Rx power that minimize oblique astigmatic and/or power errors as shown below. See, M. Jalie,
The Principles of Ophthalmic Lenses
p. 418-422 (4
th
Ed. London, 1994).
Zero Oblique
Zero Oblique Power
Astigmatism
Error
Rx
F1
F2
F1
F2
+5.0
13.02
−8.02
9.84
−4.84
+3
10.91
−7.91
8.36
−5.36
+1
9.16
−8.16
7.05
−6.05
0
8.37
−8.37
6.45
−6.45
−1
7.63
−8.63
5.88
−6.88
−5
5.04
−10.04
3.85
−8.85
Such “best form” lenses have front surfaces that are consistently steeper as the Rx becomes more positive. When referred to a fixed aperture, the front vertex height (plate height) also increases as the Rx becomes more positive. Accordingly a range of typical prescription lenses has a range of different front surfaces. It is an objective to accommodate a full range of Rx values with a single frame to a given style. It follows that even for simply formed prescription lenses, the frame carrier surface and the lens carrier surface will be coincident in one part of the prescription range only.
It is impractical in the design of frames for conventional prescription lenses to make the frame carrier surface coincident with the front surface of the lens it retains, unless the frame is of a temple bar or rimless style. An exception to this occurs for a specific group of very highly curved lenses wherein a range of different prescriptions can be satisfied at a single base curve. See U.S. Pat. No. 6,142,624 (Morris et al.). In general, however, the carrier surface will be of a generic form that allows a range of related lens surfaces to conform to the rimmed aperture outline or eye-wire.
Eyeglass frames usually sit snugly in front of the wearer's face, being spaced sufficiently therefrom to avoid physical contact whilst being stably positioned. Prescription frames have low curvature along the brow lines, typically equaling the best form base curves required for the most negative lenses of an Rx range. High minus lenses glaze flush with the frame contour and others protrude increasingly as the power is more positive, so that in general, the lens front vertex is located forward of the frame carrier surface. The choice of aperture shapes must allow the height difference between the frame carrier surface and the lens front surface to remain within a tolerance along the lens periphery that is consistent with the typical edge thickness of a lens, e.g. to within about ±0.5 mm.
Sunglass frames of the wrap-around form typically have curvature of approximately 6 to 8 D toward the temples. When prescription lenses are fitted, the substance of the inner lens surface intrudes into the space before the wearer's face. A minus lens protrudes at the temporal limits of the frame aperture, as depicted in
FIG. 1
a
. A plus power flattens the back surface of the lens, intruding against the eyelashes. In practice, wrap-around frames of currently popular styles are consistent with posterior horizontal curves between about 6 and 12 D. This limits the p
Morris Michael Alan
Perrott Colin Maurice
Burns Doane , Swecker, Mathis LLP
Mai Huy
Sola International Holdings Ltd.
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